I do believe that the Democrat's 2016 Presidential candidate said that if elected she would shut down all of the coal mines in the country.
I don't think she said, as President, she would shut down the coal mines. Here are her comments in context:
Look, we have serious economic problems in many parts of our country. And Roland is absolutely right. Instead of dividing people the way Donald Trump does, let's reunite around policies that will bring jobs and opportunities to all these underserved poor communities.
So for example, I'm the only candidate which has a policy about how to bring economic opportunity using clean renewable energy as the key into coal country. Because we're going to put a lot of coal miners and coal companies out of business, right?
And we're going to make it clear that we don't want to forget those people. Those people labored in those mines for generations, losing their health, often losing their lives to turn on our lights and power our factories.
Now we've got to move away from coal and all the other fossil fuels, but I don't want to move away from the people who did the best they could to produce the energy that we relied on.
She was talking about economic forces (like frakking) putting coal miners out of business. Which is in agreement with your statement about her lack of power to do anything directly. It was happening then and it's happened even more now. Her opponents seized on that comment to claim she would shut down coal mines. More of the usual Republican anti-Clinton smear. It never ends.
What she was really talking about was retraining those folks at something else, instead of just forgetting them and leaving them to shuffle around mostly not working as coal jobs dwindle. Renewable energy is a field that is growing as rapidly as coal is going away. Trump has done the miners a huge disservice by leading them to believe he would somehow "make coal great again" and bring back the jobs. So they don't get that retraining, and they don't get jobs.